Light-Radiating Semiconductor Component with a Luminescence Conversion Element

ABSTRACT

The light-radiating semiconductor component has a radiation-emitting semiconductor body and a luminescence conversion element. The semiconductor body emits radiation in the ultraviolet, blue and/or green spectral region and the luminescence conversion element converts a portion of the radiation into radiation of a longer wavelength. This makes it possible to produce light-emitting diodes which radiate polychromatic light, in particular white light, with only a single light-emitting semiconductor body. A particularly preferred luminescence conversion dye is YAG:Ce.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of copending International ApplicationPCT/DE97/01337, filed Jun. 26, 1997, which designated the United States.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a light-radiating semiconductor component witha semiconductor body that emits electromagnetic radiation duringoperation of the semiconductor component. The component has at least onefirst and at least one second electrical terminal, which areelectrically connected to the semiconductor body. The component furtherhas a luminescence conversion element with at least one luminescentmaterial.

A semiconductor component of that type is disclosed, for example, inGerman published patent application DE 38 04 293. There, an arrangementhaving an electroluminescent or laser diode in which the entire emissionspectrum radiated by the diode is shifted toward greater wavelengths bymeans of a plastic element that is treated with a fluorescent,light-converting organic dye. The light radiated by the arrangementconsequently has a different color from the light emitted by thelight-emitting diode. Depending on the nature of the dye added to theplastic, light-emitting diode arrangements which emit light in differentcolors can be produced using one and the same type of light-emittingdiode.

German published patent application DE 23 47 289 discloses an infrared(IR) solid-state lamp in which luminescent material is applied on theedge of an IR diode and converts the IR radiation that is radiated thereinto visible light. The aim of this measure is, for supervisorypurposes, to convert a smallest possible part of the IR radiationemitted by the diode into visible light in conjunction with the smallestpossible reduction of the intensity of the emitted IR radiation.

Furthermore, European patent application EP 486 052 discloses alight-emitting diode in which at least one semiconductorphotoluminescent layer is arranged between the substrate and an activeelectroluminescent layer. The semiconductor photoluminescent layerconverts the light of a first wavelength range—the light emitted by theactive layer in the direction of the substrate—into light of a secondwavelength range, with the result that, altogether, the light-emittingdiode emits light of different wavelength ranges.

In many potential areas of application for light-emitting diodes, suchas, for example, in display elements in motor vehicle dashboards,lighting in aircraft and automobiles, and in full-color LED displays,there is increasingly a demand for light-emitting diode arrangementswith which polychromatlc light, in particular white light, can beproduced.

Japanese patent application JP-07 176 794-A describes awhite-light-emitting, planar light source in which twoblue-light-emitting diodes are arranged at an end of a transparentplate. The diodes emit light into the transparent plate. The transparentplate is coated with a fluorescent substance on one of the two mutuallyopposite main surfaces. The fluorescent substance emits light when it isexcited by the blue light of the diodes. The light emitted by thefluorescent substance has a different wavelength from that of the bluelight emitted by the diodes. In that prior art component, it isparticularly difficult to apply the fluorescent substance in such amanner that the light source radiates homogeneous white light.Furthermore, the question of reproducibility in mass production alsoposes major problems because even slight fluctuations in the thicknessof the fluorescent layer, for example on account of unevenness of thesurface of the transparent plate, cause a change in the shade of whiteof the radiated light.

SUMMARY OF THE INVENTION

It is accordingly an object of the invention to provide alight-radiating semiconductor component, which overcomes theabove-mentioned disadvantages of the heretofore-known devices andmethods of this general type and which radiates homogeneouspolychromatic light and ensures technically simple mass production withcomponent characteristics that are reproducible to the greatest possibleextent.

With the foregoing and other objects in view there is provided, inaccordance with the invention, a light-radiating semiconductorcomponent, comprising:

a semiconductor body emitting electromagnetic radiation during anoperation of the semiconductor component, the semiconductor body havinga semiconductor layer sequence suitable for emitting electromagneticradiation of a first wavelength range selected from a spectral regionconsisting of ultraviolet, blue, and green;a first electrical terminal and a second electrical terminal eachelectrically conductively connected to the semiconductor body; anda luminescence conversion element with at least one luminescentmaterial, the luminescence conversion element converting a radiationoriginating in the first wavelength range into radiation of a secondwavelength range different from the first wavelength range, such thatthe semiconductor component emits polychromatic radiation comprisingradiation of the first wavelength range and radiation of the secondwavelength range.

The invention provides for the radiation-emitting semiconductor body tohave a layer sequence, in particular a layer sequence with an activesemiconductor layer made of Ga_(c)In_(1-x)N or Ga_(x)Al_(1-x)N, whichemits an electromagnetic radiation of a first wavelength range from theultraviolet, blue and/or green spectral region during operation of thesemiconductor component. The luminescence conversion element convertspart of the radiation originating from the first wavelength range intoradiation of a second wavelength range, in such a way that thesemiconductor component emits polychromatic radiation, in particularpolychromatic light, comprising radiation of the first wavelength rangeand radiation of the second wavelength range. This means, for example,that the luminescence conversion element spectrally selectively absorbspart of the radiation emitted by the semiconductor body, preferably onlyover a spectral subregion of the first wavelength range, and emits it inthe region of longer wavelength (in the second wavelength range).Preferably, the radiation emitted by the semiconductor body has arelative intensity maximum at a wavelength λ≦520 nm and the wavelengthrange which is spectrally selectively absorbed by the luminescenceconversion element lies outside this intensity maximum.

In accordance with an added feature of the invention, the luminescenceconversion element converts radiation of the first wavelength range intoradiation of a plurality of second wavelength ranges from mutuallydifferent spectral subregions, such that the semiconductor componentemits polychromatic radiation comprising radiation of the firstwavelength range and radiation of the plurality of second wavelengthranges. In other words, the invention advantageously makes it possiblealso to convert a number (one or more) of first spectral subregionsoriginating from the first wavelength range into a plurality of secondwavelength ranges. As a result, it is possible to produce diverse colormixtures and color temperatures.

The semiconductor component according to the invention has theparticular advantage that the wavelength spectrum generated by way ofluminescence conversion and hence the color of the radiated light do notdepend on the level of the operating current intensity through thesemiconductor body. This has great significance particularly when theambient temperature of the semiconductor component and, consequently, asis known, also the operating current intensity greatly fluctuate.Especially light-emitting diodes having a semiconductor body based onGaN are very sensitive in this respect.

In addition, the semiconductor component according to the inventionrequires only a single driving voltage and, as a result, also only asingle driving circuit configuration, whereby the outlay on devices forthe driving circuit of the semiconductor component can be kept very low.

In accordance with an additional feature of the invention, thesemiconductor component has a defined main radiating direction, and theluminescence conversion element is disposed substantially downstream ofthe semiconductor body in the main radiating direction of thesemiconductor component.

In accordance with another feature of the invention, the luminescenceconversion element is at least one luminescence conversion layerdisposed in a vicinity of the semiconductor body. In this particularlypreferred embodiment of the invention, a partially transparentluminescence conversion layer, that is to say one which is partiallytransparent to the radiation emitted by the radiation-emittingsemiconductor body, is provided as the luminescence conversion elementabove or on the semiconductor body. In order to ensure a uniform colorof the radiated light, the luminescence conversion layer isadvantageously designed in such a way that it has a constant thicknessthroughout. This has the particular advantage that the path length ofthe light radiated by the semiconductor body through the luminescenceconversion layer is virtually constant for all radiation directions. Theeffect that can be achieved as a result of this is that thesemiconductor component radiates light of the same color in alldirections. A further particular advantage of a semiconductor componentaccording to the invention in accordance with this development consistsin the fact that a high degree of reproducibility can be obtained in asimple manner, which is of considerable significance for efficient massproduction. A resist or resin layer treated with luminescent materialmay be provided, for example, as the luminescence conversion layer.

In accordance with a further feature of the invention, the luminescenceconversion element is a luminescence conversion encapsulation enclosingat least a part of the semiconductor body and partial regions of thefirst and second electrical terminals. The encapsulation is partiallytransparent and encloses at least part of the semiconductor body (andpossibly partial regions of the electrical terminals) and cansimultaneously be utilized as component encapsulation (housing). Theadvantage of a semiconductor component in accordance with thisembodiment consists essentially in the fact that conventional productionlines used for the production of conventional light-emitting diodes (forexample radial light-emitting diodes) can be utilized for itsproduction. The material of the luminescence conversion encapsulation isused for the component encapsulation instead of the transparent plasticwhich is used for this purpose in conventional light-emitting diodes.

In further advantageous embodiments of the semiconductor componentaccording to the invention and of the two preferred embodimentsmentioned above, the luminescence conversion layer or the luminescenceconversion encapsulation is composed of a transparent material, forexample plastic, preferably epoxy resin, which is provided with at leastone luminescent material (examples of preferred plastics and luminescentmaterials will be found further below). In this way, it is possible toproduce luminescence conversion elements in a particularlycost-effective manner. Specifically, the requisite process steps can beintegrated in conventional production lines for light-emitting diodeswith no major outlay.

In accordance with again an added feature of the invention, the secondwavelength range includes wavelengths at least some of which are longerthan wavelengths of the first wavelength range.

In accordance with again an additional feature of the invention, thesemiconductor body is adapted to emit ultraviolet radiation duringoperation of the semiconductor component, and the luminescenceconversion element converts at least a portion of the ultravioletradiation into visible light.

In accordance with again another feature of the invention, the firstwavelength range and the second wavelength range of the polychromaticradiation lie at least partially in mutually complementary-colorspectral regions, and a combination of radiation from the first andsecond wavelength range results in white light.

When the second spectral subregion of the first wavelength range and asecond wavelength range are complementary to one another, it is possibleto produce polychromatic, in particular white, light from a singlecolored light source, in particular a light-emitting diode having asingle blue-light-radiating semiconductor body. In order, for example,to produce white light with a blue-light-emitting semiconductor body,part of the radiation from the blue spectral region emitted by thesemiconductor body is converted into the yellow spectral region, whichis complementarily colored with respect to blue. The color temperatureor color locus of the white light can in this case be varied by asuitable choice of the luminescence conversion element, in particular bya suitable choice of the luminescent material, its particle size and itsconcentration. Furthermore, these arrangements also advantageouslyafford the possibility of using luminescent material mixtures, as aresult of which, advantageously, the desired hue can be set veryaccurately. Likewise, it is possible to configure luminescenceconversion elements inhomogeneously, for example by means ofinhomogeneous luminescent material distribution. Different path lengthsof the light through the luminescence conversion element canadvantageously be compensated for as a result of this.

In accordance with again a further feature of the invention, the firstwavelength range emitted by the semiconductor body and two secondwavelength ranges produce an additive color triad, such that white lightis radiated by the semiconductor component during operation thereof.

In a further preferred embodiment of the semiconductor componentaccording to the invention, the luminescence conversion element oranother constituent of a component encapsulation has, for the purpose ofcolor matching, one or more dyes which do not effect wavelengthconversion. For this purpose, it is possible to use the dyes which areused for the production of conventional light-emitting diodes, such as,for example, azo, anthraquinone or perinone dyes.

In order to protect the luminescence conversion element against anexcessively high radiation load, in an advantageous development or inthe above-mentioned preferred embodiments of the semiconductor componentaccording to the invention, at least part of the surface of thesemiconductor body is surrounded by a first, transparent casingcomposed, for example, of a plastic, on which casing the luminescenceconversion layer is applied. This reduces the radiation density in theluminescence conversion element and, consequently, the radiation loadthereof, which, depending on the materials used, has a positive effecton the life of the luminescence conversion element.

In accordance with yet an added feature of the invention, the radiationemitted by the semiconductor body has a luminescence intensity maximumin a blue spectral region at a wavelength selected from the groupconsisting of λ=430 nm and λ=450 nm. The preferred radiation-emittingsemiconductor body has a radiation spectrum with an intensity maximum ata wavelength of between 420 nm and 460 nm, in particular at 430 nm (forexample semiconductor body based on Ga_(x)Al_(1-x)N) or 450 nm (forexample semiconductor body based on Ga_(x)In_(1-x)N). It is advantageousthat virtually all colors and mixed colors of the C.I.E. chromaticitydiagram can be produced by such a semiconductor component according tothe invention. In this case, as specified above, the radiation-emittingsemiconductor body may essentially be composed of electroluminescentsemiconductor material, but also of a different electroluminescentmaterial, such as polymer material, for example.

In accordance with yet an additional feature of the invention, an opaquebase housing is formed with a recess, and wherein the semiconductor bodyis disposed in the recess of the base housing, and including a coveringlayer having a luminescence conversion layer on the recess.Alternatively, the recess is at least partially filled with theluminescence conversion element.

In accordance with yet another feature of the invention, theluminescence conversion element comprises a plurality of layers withmutually different wavelength conversion properties.

In accordance with yet a further feature of the invention, theluminescence conversion element includes organic dye molecules in aplastic matrix, such as in a matrix of silicone, thermoplastic material,or thermosetting plastic material. The luminescence conversion elementmay also have organic dye molecules in an epoxy resin matrix or apolymethyl methacrylate matrix.

In accordance with yet again an added feature of the invention, theluminescence conversion element has at least one inorganic luminescencematerial selected from the group of phosphors. The inorganic luminescentmaterial is preferably from the group of Ce-doped garnets, such asYAG:Ce.

In accordance with yet again an additional feature of the invention, theinorganic luminescent material is embedded in an epoxy resin matrix. Itmay also be embedded in a matrix formed of inorganic glass with arelatively low melting point.

Preferably, the inorganic luminescent material has a mean particle sizeof approximately 10 μm.

In accordance with yet again another feature of the invention, theluminescence conversion element is provided with a plurality of mutuallydifferent materials selected from the group consisting of organic andinorganic luminescent materials. The luminescence conversion element mayinclude organic or inorganic dye molecules partly with and partlywithout a wavelength conversion effect.

In accordance with yet again a further feature of the invention, theluminescence conversion element includes light-diffusing particles. Thecomponent may also have a transparent encapsulation with light-diffusingparticles.

In accordance with again an added feature of the invention, theluminescence conversion element comprises at least one luminescent4f-organometallic compound.

A blue output radiation is obtained if, in accordance with theinvention, the luminescence conversion element includes a luminescentmaterial that is luminescent in a blue region. The encapsulation maythereby be transparent with a blue luminescent material.

As noted, the luminescence conversion encapsulation or the luminescenceconversion layer may be produced from a resist or from a plastic, forexample from a silicone, thermoplastic or thermosetting plastic material(epoxy and acrylate resins) used for the encapsulation of optoelectroniccomponents. Furthermore, covering elements fabricated from thermoplasticmaterials, for example, can be used as the luminescence conversionencapsulation. All the above-mentioned materials can be treated with oneor more luminescent materials in a simple manner.

A semiconductor component according to the invention can be realized ina particularly simple manner when the semiconductor body is arranged ina recess in an optionally prefabricated housing and the recess isprovided with a covering element having the luminescence conversionlayer. A semiconductor component of this type can be produced in largenumbers in conventional production lines. For this purpose, all that isnecessary, after the mounting of the semiconductor body in the housing,is to apply the covering element, for example a resist or casting resinlayer or a prefabricated covering plate made of thermoplastic material,to the housing. Optionally, the recess in the housing may be filled witha transparent material, for example a transparent plastic, which doesnot alter in particular the wavelength of the light emitted by thesemiconductor body or, however, if desired, may already be designed suchthat it effects luminescence conversion.

In a development of the semiconductor component according to theinvention which is particularly preferred on account of the fact that itcan be realized in a particularly simple manner, the semiconductor bodyis arranged in a recess in a housing which is optionally prefabricatedand may already be provided with a lead frame and the recess is filledwith an at least partially transparent casting resin, to which theluminescent material has already been added prior to the recess beingsealed by casting. In this case, the luminescence conversion element isconsequently provided by the potting of the semiconductor body that isprovided with luminescent material.

A particularly preferred material for the production of the luminescenceconversion element is epoxy resin, to which one or more luminescentmaterials are added. However, it is also possible to use polymethylmethacrylate (PMMA) instead of epoxy resin.

PMMA can be treated with organic dye molecules in a simple manner.Perylene-based dye molecules, for example, can be used to producegreen-, yellow- and red-light-emitting semiconductor componentsaccording to the invention. Semiconductor components which emit light inthe UV, visible or infrared region can also be produced by admixture of4f-organometallic compounds. In particular, red-light-emittingsemiconductor components according to the invention can be realized forexample by admixture of Eu³⁺-based organometallic chelates (λ≈620 nm).Infrared-radiating semiconductor components according to the invention,in particular having blue-light-emitting semiconductor bodies, can beproduced by admixture of 4f-chelates or of Ti³⁺-doped sapphire.

A white-light-radiating semiconductor component according to theinvention can advantageously be produced by choosing the luminescentmaterial such that a blue radiation emitted by the semiconductor body isconverted into complementary wavelength ranges, in particular blue andyellow, or to form additive color triads, for example blue, green andred. In this case, the yellow or the green and red light is produced bymeans of the luminescent materials. The hue (color locus in the CIEchromaticity diagram) of the white light thereby produced can in thiscase be varied by a suitable choice of the dye/s in respect of mixtureand concentration.

Suitable organic luminescent materials for a white-light-radiatingsemiconductor component according to the invention are peryleneluminescent materials, such as, for example, BASF Lumogen F 083 forgreen luminescence, BASF Lumogen F 240 for yellow luminescence and BASFLumogen F 300 for red luminescence. These dyes can be added totransparent epoxy resin, for example, in a simple manner.

A preferred method for producing a green-light-emitting semiconductorcomponent using a blue-light-radiating semiconductor body consists inusing UO₂ ⁺⁺-substituted borosilicate glass for the luminescenceconversion element.

In a further preferred development of a semiconductor componentaccording to the invention and of the advantageous embodiments specifiedabove, light-diffusing particles, so-called diffusers, are additionallyadded to the luminescence conversion element or to anotherradiation-transmissive component of the component encapsulation. Thecolor perception and the radiation characteristics of the semiconductorcomponent can advantageously be optimized by this means.

In a particularly advantageous embodiment of the semiconductor componentaccording to the invention, the luminescence conversion element is atleast partially composed of a transparent epoxy resin provided with aninorganic luminescent material. Specifically, it is advantageous thatinorganic luminescent materials can be bound in epoxy resin in a simplemanner. A particularly preferred inorganic luminescent material for theproduction of white-light-emitting semiconductor components according tothe invention is the phosphor YAG:Ce (Y₃Al₅O₁₂:Ce³⁺). The latter can bemixed in a particularly simple manner in transparent epoxy resins whichare conventionally used in LED technology. Other conceivable luminescentmaterials are further garnets doped with rare earths, such as, forexample, Y₃GasO₁₂:Ce³⁺, Y (Al,Ga)₅O₁₂:Ce³⁺ and Y(Al,Ga)₅O₁₂:Tb³⁺, aswell as alkaline earth metal sulfides doped with rare earths, such as,for example, SrS:Ce³⁺, Na, SrS:Ce³⁺, Cl, Srs:CeCl₃, CaS:Ce³⁺ andSrSe:Ce³⁺.

Furthermore, the thiogallates doped with rare earths, such as, forexample, CaGa₂S₄:Ce³⁺ and SrGa₂S₄:Ce³⁺, are particularly suitable forthe purpose of producing differently polychromatic light. The use ofaluminates doped with rare earths, such as, for example, YAlO₃:Ce³⁺,YGaO₃:Ce³⁺, Y(Al,Ga)O₃:Ce³⁺, and orthosilicates M₂SiO₅:Ce³⁺ (M:Sc, Y,Sc) doped with rare earths, such as, for example, Y₂SiO₅:Ce³⁺, islikewise conceivable for this purpose. In all of the yttrium compounds,the yttrium can, in principle, also be replaced by scandium orlanthanum.

In a further possible embodiment of the semiconductor componentaccording to the invention, at least all those components of theencapsulation through which light is radiated, that is to say includingthe luminescence conversion encapsulation or layer, are composed ofpurely inorganic materials. Consequently, the luminescence conversionelement is composed of an inorganic luminescent material which isembedded in a thermally stable, transparent or partially transparentinorganic material. In particular, the luminescence conversion elementis composed of an inorganic phosphor, which is embedded in an inorganicglass advantageously of low melting point (for example silicate glass).A preferred procedure for producing a luminescence conversion layer ofthis type is the sol gel technique, by means of which the entireluminescence conversion layer, that is to say both the inorganicluminescent material and the embedding material, can be produced in onework operation.

In order to improve the thorough mixing of the radiation of the firstwavelength range that is emitted by the semiconductor body with theluminescence-converted radiation of the second wavelength range andhence the color homogeneity of the radiated light, in an advantageousrefinement of the semiconductor component according to the invention, adye which emits light in the blue region is additionally added to theluminescence encapsulation or the luminescence conversion layer and/orto another component of the component encapsulation, which dyeattenuates a so-called directional characteristic of the radiationradiated by the semiconductor body. Directional characteristic is to beunderstood to mean that the radiation emitted by the semiconductor bodyhas a preferred radiation direction.

In a preferred refinement of the semiconductor component according tothe invention, the inorganic luminescent material is used in powder formfor the above-mentioned purpose of thorough mixing of the emittedradiation, the luminescent material particles not dissolving in thesubstance (matrix) encapsulating them. In addition, the inorganicluminescent material and the substance encapsulating it have mutuallydifferent refractive indices. This advantageously leads to a portion ofthe light which is not absorbed by the luminescent material beingscattered, in a manner dependent on the particle size of the luminescentmaterial. The directional characteristic of the radiation radiated bythe semiconductor body is thereby efficiently attenuated, with theresult that the unabsorbed radiation and the luminescence-convertedradiation are homogeneously mixed, which leads to a spatiallyhomogeneous color perception.

A white-light-radiating semiconductor component according to theinvention can particularly preferably be realized by admixing theinorganic luminescent material YAG:Ce (Y₃Al₅O₁₂:CE³⁺) with an epoxyresin used to produce the luminescence conversion encapsulation orlayer. Part of a blue radiation emitted by the semiconductor body isshifted by the inorganic luminescent material Y₃Al₅O₁₂:CE³⁺ into theyellow spectral region and, consequently, into a wavelength range whichis complementarily colored with respect to the color blue. The hue(color locus) in the CIE chromaticity diagram) of the white light can inthis case be varied by a suitable choice of the dye mixture andconcentration.

The inorganic luminescent material YAG:Ce has, inter alia, theparticular advantage that insoluble coloring pigments (particle size inthe region of 10 mm) having a refractive index of approximately 1.84 areinvolved in this case. Consequently, not only does the wavelengthconversion occur but also a scattering effect which leads to good mixingtogether of blue diode radiation and yellow converter radiation.

In a further preferred development of a semiconductor componentaccording to the invention and of the advantageous embodiments specifiedabove, light-diffusing particles, so-called diffusers, are additionallyadded to the luminescence conversion element or to anotherradiation-transmissive component of the component encapsulation. Thecolor perception and the radiation characteristic of the semiconductorcomponent can advantageously be further improved by this means.

It is particularly advantageous that the luminous efficiency ofwhite-light-emitting semiconductor components according to the inventionand their above-mentioned embodiments having a blue-light-emittingsemiconductor body produced essentially on the basis of GaN iscomparable with the luminous efficiency of an incandescent bulb. Thereason for this is that, on the one hand, the external quantumefficiency of such semiconductor bodies is a few percent and, on theother hand, the luminescence efficiency of organic dye molecules isoften established at more than 90%. Furthermore, the semiconductorcomponent according to the invention is distinguished by an extremelylong life, greater robustness and a smaller operating voltage incomparison with the incandescent bulb.

It is advantageous, moreover, that the luminosity of the semiconductorcomponent according to the invention that is perceptible to the humaneye can be distinctly increased by comparison with a semiconductorcomponent which is not equipped with the luminescence conversion elementbut is otherwise identical, since the sensitivity of the eye increasesin the direction of a higher wavelength.

Furthermore, the principle according to the invention can advantageouslybe used also to convert an ultraviolet radiation which is emitted by thesemiconductor body in addition to the visible radiation into visiblelight. The luminosity of the light emitted by the semiconductor body isthereby distinctly increased.

The concept, presented here, of luminescence conversion with blue lightfrom a semiconductor body can advantageously be extended to multistageluminescence conversion elements as well, in accordance with the schemeultraviolet→blue→green→yellow→red. In this case, a plurality ofspectrally selectively emitting luminescence conversion elements arearranged one after the other relative to the semiconductor body.

Likewise, it is advantageously possible for a plurality of differentlyspectrally selectively emitting dye molecules to be jointly embedded ina transparent plastic of a luminescence conversion element. A very broadcolor spectrum can be produced by this means.

A particular advantage of white-light-radiating semiconductor componentsaccording to the invention in which YAG:Ce, in particular, is used asthe luminescence conversion dye consists in the fact that thisluminescent material, upon excitation by blue light, effects a spectralshift of approximately 100 nm between absorption and emission. Thisleads to a significant reduction in the reabsorption of the lightemitted by the luminescent material and hence to a higher luminousefficiency. In addition, YAG:Ce advantageously has high thermal andphotochemical (for example UV) stability (significantly higher thanorganic luminescent materials), with the result that it is even possibleto produce white-light-emitting diodes for outdoor use and/or hightemperature ranges.

YAG:Ce has, to date, proved to be the best-suited luminescent materialin respect of reabsorption, luminous efficiency, thermal andphotochemical stability and processability. However, the use of otherCe-doped phosphors is also conceivable, in particular of Ce-dopedgarnets.

In a particularly advantageous manner, semiconductor componentsaccording to the invention can be used, in particular on account oftheir low power consumption, in full-color LED displays for the lightingof motor vehicle interiors or of aircraft cabins as well as for theillumination of display devices such as motor vehicle dashboards orliquid crystal displays.

Other features which are considered as characteristic for the inventionare set forth in the appended claims.

Although the invention is illustrated and described herein as embodiedin a light-radiating semiconductor component having a luminescenceconversion element, it is nevertheless not intended to be limited to thedetails shown, since various modifications and structural changes may bemade therein without departing from the spirit of the invention andwithin the scope and range of equivalents of the claims.

The construction and method of operation of the invention, however,together with additional objects and advantages thereof will be bestunderstood from the following description of specific embodiments whenread in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic sectional side view of a first exemplaryembodiment of a semiconductor component according to the invention;

FIG. 2 is a diagrammatic sectional side view of a second exemplaryembodiment of the semiconductor component according to the invention;

FIG. 3 is a diagrammatic sectional side view of a third exemplaryembodiment of the semiconductor component according to the invention;

FIG. 4 is a diagrammatic sectional side view of a fourth exemplaryembodiment of the semiconductor component according to the invention;

FIG. 5 is a diagrammatic sectional side view of a fifth exemplaryembodiment of the semiconductor component according to the invention;

FIG. 6 is a diagrammatic sectional side view of a sixth exemplaryembodiment of the semiconductor component according to the invention;

FIG. 7 is a graph of an emission spectrum of a blue-light-radiatingsemiconductor body with a layer sequence based on GaN;

FIG. 8 is a graph of the emission spectra of two semiconductorcomponents according to the invention which radiate white light;

FIG. 9 is a diagrammatic sectional view taken through a semiconductorbody which emits blue light;

FIG. 10 is a diagrammatic sectional side view of a seventh exemplaryembodiment of the semiconductor component according to the invention;

FIG. 11 is a graph of an emission spectrum of a semiconductor componentaccording to the invention which radiates polychromatic red light;

FIG. 12 is a graph of the emission spectra of further semiconductorcomponents according to the invention which radiate white light;

FIG. 13 is a diagrammatic sectional side view of an eighth exemplaryembodiment of the semiconductor component according to the invention;and

FIG. 14 is a diagrammatic sectional side view of a ninth exemplaryembodiment of the semiconductor component according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be had to the figures of the drawing in detail, inwhich identical or functionally identical parts are designated by thesame reference symbols throughout, and first, particularly, to FIG. 1thereof.

The light-emitting semiconductor component illustrated in FIG. 1, asemiconductor body 1 has a back-side contact 11, a front-side contact 12and a layer sequence 7, which is composed of a number of differentlayers and has at least one active zone which emits a radiation (forexample ultraviolet, blue or green) during the operation of thesemiconductor component.

An example of a suitable layer sequence 7 for this and for all of theexemplary embodiments described below is shown in FIG. 9. There, a layersequence made of an AlN or GaN layer 19, an n-conducting GaN layer 20,an n-conducting Ga_(x)Al_(1-x)N or Ga_(x)In_(1-x)N layer 21, a furthern-conducting GaN or a Ga_(x)In_(1-x)N layer 22, a p-conductingGa_(x)Al_(1-x)N layer or Ga_(x)In_(1-x)N layer 23 and a p-conducting GaNlayer 24 is applied on a substrate 18 composed of SiC, for example. Arespective contact metallization layer 27, 28 is applied on a mainsurface 25 of the p-conducting GaN layer 24 and a main surface 26 of thesubstrate 18, said contact metallization layer being composed of amaterial which is conventionally used for electrical contacts inopto-semiconductor technology.

However, it is also possible to use any other semiconductor body deemedto be suitable by those skilled in this art for the semiconductorcomponent according to the invention. This likewise applies to all ofthe exemplary embodiments described below.

In the exemplary embodiment of FIG. 1, the semiconductor body 1 is fixedby its back-side contact 11 on a first electrical terminal 2 by means ofan electrically conductive bonding agent, for example a metallic solderof an adhesive. The front-side contact 12 is connected to a secondelectrical terminal 3 by means of a bonding wire 14.

The free surfaces of the semiconductor body 1 and partial regions of theelectrical terminals 2 and 3 are directly enclosed by a luminescenceconversion encapsulation 5. The latter is preferably composed of atransparent plastic (preferably epoxy resin or else polymethylmethacrylate) which can be used for transparent light-emitting diodeencapsulations and is treated with luminescent material 6, preferablyinorganic luminescent material, for white-light-emitting components,preferably Y₃Al₅O₁₂:Ce³⁺ (YAG:Ce).

The exemplary embodiment of a semiconductor component according to theinvention which is illustrated in FIG. 2 differs from that of FIG. 1 bythe fact that the semiconductor body 1 and partial regions of theelectrical terminals 2 and 3 are enclosed by a transparent encapsulation15 instead of by a luminescence conversion encapsulation. Thistransparent encapsulation 15 does not effect any wavelength change inthe radiation emitted by the semiconductor body 1 and is composed, forexample, of an epoxy, silicone or acrylate resin which is conventionallyused in light-emitting diode technology, or of another suitableradiation-transmissive material, such as inorganic glass, for example.

A luminescence conversion layer 4 is applied to the transparentencapsulation 15 and, as illustrated in FIG. 2, covers the entiresurface of the encapsulation 15. It is likewise conceivable for theluminescence conversion layer 4 to cover only a partial region of thissurface. The luminescence conversion layer 4 is composed, for example,once again of a transparent plastic (for example epoxy resin, resist orpolymethyl methacrylate) which is treated with a luminescent material 6.In this case, too, YAG:Ce is preferably suitable as luminescent materialfor a white-light-emitting semiconductor component.

This exemplary embodiment has the particular advantage that the pathlength through the luminescence conversion element is approximately thesame size for all of the radiation emitted by the semiconductor body.This is important particularly when, as is often the case, the exact hueof the light radiated by the semiconductor component depends on thispath length.

For improved output coupling of the light from the luminescenceconversion layer 4 of FIG. 2, a covering 29 (depicted by a broken line)in the form of a lens can be provided on a side surface of thecomponent, which covering reduces total reflection of the radiationwithin the luminescence conversion layer 4. This covering 29 in the formof a lens may be composed of transparent plastic or glass and be bonded,for example, onto the luminescence conversion layer 4 or be designeddirectly as the component part of the luminescence conversion layer 4.

In the exemplary embodiment illustrated in FIG. 3, the first and secondelectrical terminals 2, 3 are embedded in an opaque, possiblyprefabricated base housing 8 having a recess 9. “Prefabricated” is to beunderstood to mean that the base housing 8 is already preconstructed onthe connections 2, 3, for example by means of injection molding, beforethe semiconductor body is mounted on to the connection 2. The basehousing 8 is composed for example of an opaque plastic and the recess 9is designed, in respect of its shape, as a reflector 17 for theradiation emitted by the semiconductor body during operation (ifappropriate by suitable coating of the inner walls of the recess 9).Such base housings 8 are used in particular in the case oflight-emitting diodes which can be surface-mounted on printed circuitboards. They are applied to a lead frame having the electrical terminals2, 3, for example by means of injection molding, prior to the mountingof the semiconductor bodies.

The recess 9 is covered by a luminescence conversion layer 4, forexample a separately produced covering plate 17 made of plastic which isfixed on the base housing 8. Suitable materials for the luminescenceconversion layer 4 are once again, as mentioned further above in thegeneral part of the description, the plastics or inorganic glass inconjunction with the luminescent materials mentioned there. The recess 9may either be filled with a transparent plastic, with an inorganic glassor with gas or else be provided with a vacuum.

As in the case of the exemplary embodiment according to FIG. 2, acovering 29 (depicted by a broken line) in the form of a lens can beprovided on the luminescence conversion layer 4 in this case as well,for improved output coupling of the light from said luminescenceconversion layer, which covering reduces total reflection of theradiation within the luminescence conversion layer 4. This covering 29may be composed of transparent plastic and be bonded, for example, ontothe luminescence conversion layer 4 or be designed integrally togetherwith the luminescence conversion layer 4.

In a particularly preferred embodiment, the recess 9 is filled, as shownin FIG. 10, with an epoxy resin provided with luminescent material, thatis to say with a luminescence encapsulation 5 which forms theluminescence conversion element. A covering plate 17 and/or a covering29 in the form of a lens can then be omitted as well. Furthermore, asillustrated in FIG. 13, the first electrical terminal 2 is optionallydesigned as a reflector well 34 for example by embossing in the regionof the semiconductor body 1, which reflector well is filled with aluminescence conversion encapsulation 5.

In FIG. 4, a so-called radial diode is illustrated as a furtherexemplary embodiment. In this case, the semiconductor body 1 is fixed ina part 16, designed as a reflector, of the first electrical terminal 2by means of soldering or bonding, for example. Such housing designs areknown in light-emitting diode technology and, therefore, need not beexplained in any further detail.

In the exemplary embodiment of FIG. 4, the semiconductor body 1 issurrounded by a transparent encapsulation 15 which, as in the case ofthe second exemplary embodiment mentioned (FIG. 2), does not effect anywavelength change in the radiation emitted by the semiconductor body 1and may be composed, for example, of a transparent epoxy resin which isconventionally used in light-emitting diode technology or of organicglass.

A luminescence conversion layer 4 is applied on this transparentencapsulation 15. Suitable materials for this are, for example, onceagain, as referred to in connection with the above-mentioned exemplaryembodiments, the plastics or inorganic glass in conjunction with thedyes mentioned there.

The entire structure, comprising semiconductor body 1, partial regionsof the electrical terminals 2, 3, transparent encapsulation 15 andluminescence conversion layer 4, is directly enclosed by a furthertransparent encapsulation 10, which does not effect any wavelengthchange in the radiation which has passed through the luminescenceconversion layer 4. It is composed, for example, once again of atransparent epoxy resin which is conventionally used in light-emittingdiode technology or of inorganic glass.

The exemplary embodiment shown in FIG. 5 differs from that of FIG. 4essentially by the fact that the free surfaces of the semiconductor body1 are directly covered by a luminescence conversion encapsulation 5,which is again surrounded by a further transparent encapsulation 10.FIG. 5 illustrates, moreover, by way of example, a semiconductor body 1in which, instead of the underside contacts, a further contact isprovided on the semiconductor layer sequence 7, which further contact isconnected to the associated electrical terminal 2 or 3 by means of asecond bonding wire 14. It goes without saying that such semiconductorbodies 1 can also be used in all the other exemplary embodimentsdescribed herein. Conversely, of course, a semiconductor body 1 inaccordance with the above-mentioned exemplary embodiments can also beused in the exemplary embodiment of FIG. 5.

For the sake of completeness, let it be noted at this point that anintegral luminescence conversion encapsulation 5, which then replacesthe combination of luminescence conversion encapsulation 5 and furthertransparent encapsulation 10, can, of course, also be used in the designaccording to FIG. 5 in an analogous manner to the exemplary embodimentaccording to FIG. 1.

In the case of the exemplary embodiment of FIG. 6, a luminescenceconversion layer 4 (possible materials as specified above) is applieddirectly to the semiconductor body 1. The latter and partial regions ofthe electrical terminals 2, 3 are enclosed by a further transparentencapsulation 10, which does not effect any wavelength change in theradiation which has passed through the luminescence conversion layer 4,and is fabricated for example from a transparent epoxy resin which canbe used in light-emitting diode technology or from glass.

Such semiconductor bodies 1 provided with a luminescence conversionlayer 4 and not having an encapsulation can, of course, advantageouslybe used in all housing designs known from light-emitting diodetechnology (for example SMD housings, radial housings (cf. FIG. 5)).

In the case of the exemplary embodiment of a semiconductor componentaccording to the invention which is illustrated in FIG. 14, atransparent well part 35 is arranged on the semiconductor body 1 and hasa well 36 above the semiconductor body 1. The well part 35 is composedfor example of transparent epoxy resin or of inorganic glass and isfabricated for example by means of injection-molding encapsulation ofthe electrical terminals 2, 3 including semiconductor body 1. Arrangedin this well 36 is a luminescence conversion layer 4, which, forexample, is once again fabricated from epoxy resin or inorganic glass inwhich are bound particles 37, composed of one of the above-mentionedinorganic luminescent materials. In the case of this design, it isadvantageously ensured in a very simple manner that the luminescentmaterial accumulates at unintended locations, for example next to thesemiconductor body, during the production of the semiconductorcomponent. Of course, the well part 35 can also be produced separatelyand be fixed in a different way, for example on a housing part, abovethe semiconductor body 1.

In all of the exemplary embodiments described above, it is possible, inorder to optimize the color perception of the radiated light and also inorder to adapt the radiation characteristic, for the luminescenceconversion element (luminescence conversion encapsulation 5 orluminescence conversion layer 4), if appropriate the transparentencapsulation 15, and/or if appropriate the further transparentencapsulation 10 to have light-diffusing particles, advantageouslyso-called diffusers. Examples of such diffusers are mineral fillers, inparticular CaF₂, TiO₂, SiO₂, CaCO₃ or BaSO₄ or else organic pigments.These materials can be added in a simple manner to the above-mentionedplastics.

FIGS. 7, 8 and 12 respectively show emission spectra of ablue-light-radiating semiconductor body (FIG. 7) (luminescence maximumat λ≈430 nm) and of white-light-emitting semiconductor componentsaccording to the invention which are produced by means of such asemiconductor body (FIGS. 8 and 12). The wavelength l in nm is plottedin each case on the abscissa and a relative electroluminescence (EL)intensity is in each case plotted on the ordinate.

Only part of the radiation emitted by the semiconductor body accordingto FIG. 7 is converted into a wavelength range of longer wavelength,with the result that white light is produced as mixed color. The dashedline 30 in FIG. 8 represents an emission spectrum of a semiconductorcomponent according to the invention which emits radiation from twocomplementary wavelength ranges (blue and yellow) and hence white lightoverall. In this case, the emission spectrum has a respective maximum atwavelengths of between approximately 400 and approximately 430 nm (blue)and of between approximately 550 and approximately 580 nm (yellow). Thesolid line 31 represents the emission spectrum of a semiconductorcomponent according to the invention which mixes the color white fromthree wavelength ranges (additive color triad formed from blue, greenand red). In this case, the emission spectrum has a respective maximumfor example at the wavelengths of approximately 430 nm (blue),approximately 500 nm (green) and approximately 615 nm (red).

Furthermore, FIG. 11 illustrates an emission spectrum of a semiconductorcomponent according to the invention which radiates polychromatic lightcomprising blue light (maximum at a wavelength of approximately 470 nm)and red light (maximum at a wavelength of approximately 620 nm). Theoverall color perception of the radiated light for the human eye ismagenta. The emission spectrum radiated by the semiconductor body inthis case corresponds once again to that of FIG. 7.

FIG. 12 shows a white-light-emitting semiconductor component accordingto the invention which is provided with a semiconductor body emitting anemission spectrum in accordance with FIG. 7 and in which YAG:Ce is usedas the luminescence material. Only part of the radiation emitted by thesemiconductor body in accordance with FIG. 7 is converted into awavelength range of longer wavelength, with the result that white lightis produced as the mixed color. The differently dashed lines 30 to 33 ofFIG. 12 represent emission spectra of semiconductor components accordingto the invention in which the luminescence conversion element, in thiscase a luminescence conversion encapsulation made of epoxy resin, hasdifferent YAG:Ce concentrations. Each emission spectrum has a respectiveintensity maximum between λ=420 nm and λ=430 nm, that is to say in theblue spectral region and between λ=520 nm and λ=545 nm, that is to sayin the green spectral region, the emission bands having thelonger-wavelength intensity maximum largely lying in the yellow spectralregion. The diagram of FIG. 12 makes it clear that in the semiconductorcomponent according to the invention, the CIE color locus of the whitelight can be altered in a simple manner by alteration of the luminescentmaterial concentration in the epoxy resin.

Furthermore, it is possible to apply inorganic luminescent materialsbased on Ce-doped garnets, thiogallates, alkaline earth metal sulfidesand aluminates directly to the semiconductor body, without dispersingthem in epoxy resin or glass.

A further particular advantage of the above-mentioned inorganicluminescent materials results from the fact that, unlike in the case oforganic dyes, the luminescent material concentration e.g. in the epoxyresin is not limited by the solubility. As a result, large thicknessesof luminescence conversion elements are not necessary.

The explanation of the semiconductor component according to theinvention using the exemplary embodiments described above ought not, ofcourse, to be regarded as a restriction of the invention thereto. Forexample, a polymer LED emitting a corresponding radiation spectrum mayalso be understood as semiconductor body, such as, for example,light-emitting diode chips or laser diode chips.

1. A light-radiating semiconductor component, comprising: asemiconductor body emitting electromagnetic radiation during anoperation of the semiconductor component, said semiconductor body havinga semiconductor layer sequence suitable for emitting electromagneticradiation of a first wavelength range selected from a spectral regionconsisting of ultraviolet, blue, and green; a first electrical terminaland a second electrical terminal each electrically conductivelyconnected to said semiconductor body; a luminescence conversion elementwith at least one luminescent material, said luminescence conversionelement converting a radiation originating in the first wavelength rangeinto radiation of a second wavelength range different from the firstwavelength range, such that the semiconductor component emitspolychromatic radiation comprising radiation of the first wavelengthrange and radiation of the second wavelength range. 2-33. (canceled)